patch-delta: use size_t for sizes
`patch_delta()` takes the source and delta sizes by value and writes back the reconstructed target size through an `unsigned long *`. That datatype cannot represent a value that exceeds 4 GiB on systems where `unsigned long` is 32-bit (notably 64-bit Windows builds), though, even though the delta encoding itself, the on-disk layout, and the in-memory buffers happily carry such sizes. A `size_t` companion to `get_delta_hdr_size()`, `get_delta_hdr_size_sz()`, was introduced in 17fa077596 (delta, packfile: use size_t for delta header sizes, 2026-05-08) precisely so that `patch_delta()` could be widened without changing the on-the-wire decoding helper's signature. Widen `patch_delta()`'s three size parameters to `size_t` and switch its internal use of `get_delta_hdr_size()` to the `_sz` variant. Then propagate the wider type through the callers. Assisted-by: Opus 4.7 Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>